In liquid laundry detergent compositions, especially those for the washing of textile fabrics, it is common to include one or more soap and/or non-soap surfactant materials for assisting removal of various kinds of soil.
It is also common to add one or more perfume components to liquid laundry detergent compositions so as to render such compositions as well as the fabrics treated with them an attractive smell.
Nowadays, more and more detergent liquids are coloured and are sold in transparent bottles because this has proven to be appealing to the customer. Hence, the colour stability of detergent liquids has become significantly more important in recent times.
EP-A-380,406 discloses a liquid laundry detergent composition containing non-soap surfactant material, coconut fatty acid soap, a perfume and a dye material. Furthermore, WO-88/03162 discloses a liquid laundry detergent composition containing non-soap surfactant material, fatty acid soap based on an oleic acid/coconut fatty acid mixture and a mixture of perfume, dye, opacifying agent and optical brightener. A rather similar type of liquid laundry detergent composition comprising non-soap surfactant, palm kernel fatty acid soap and a mixture of perfume, dye preservative and polymer is disclosed in EP-A-592,947. Furthermore, U.S. Pat. No. 4,077,911 discloses a colored liquid detergent composition containing a colorant of the coal-tar type and butylated hydroxytoluene.
We have now found that perfumes in combination with fatty acid soaps generally can have a negative influence on the dye present in the liquid detergent composition. In particular, we have found that perfumes in combination with fatty acid soaps with at least some degree of unsaturation can have a significant negative effect on colour of the composition, during prolonged storage of the liquid laundry detergent composition, particularly if said composition also contains an enzyme.
In view of this, it is an object of the present invention to provide a liquid laundry detergent composition containing a fatty acid soap, a perfume composition, a dye material and an enzyme, wherein the colour of the composition is not negatively effected during prolonged storage, particularly when stored in sunlight.
We have surprisingly found that this object can be achieved by adding an anti-oxidant to said liquid laundry detergent composition. In other words, we have found that a dye-containing liquid laundry detergent composition which further contains a fatty acid soap, a perfume composition and an enzyme, and wherein the characteristics of the dye do not deteriorate during storage, can be obtained when that composition further contains an antioxidant as further specified in the claims.
It should be noted in this connection that the dye deterioration is not only induced by exposure of light but can also occur in the dark as well as when storing the composition at higher temperatures. Without wishing to be bound by any theory, it is postulated that the dyes do not produce stable colours probably due to oxidative processes that can—at least—be reduced by the addition of an antioxidant.
Definition of the Invention
Accordingly, in one aspect the present invention provides a liquid laundry detergent composition comprising:                (a) from 5% to 70% by weight of surfactant material other than fatty acid soap;        (b) from 1% to 20% by weight of a fatty acid soap having from 12 to 20 C atoms;        (c) from 0.01% to 3% by weight of a perfume composition;        (d) an effective amount of a water soluble dye material;        (e) an effective amount of an enzyme; and        (f) from 0.001% to 2% by weight of an antioxidant selected from the group consisting of an alkylated phenol (as defined herein) α-, β-, γ-, δ-tocopherol, ethoxyquine, 2,2,4-trimethyl-1,2-dihydroquinoline, 2,6-di-tert-butyl hydroquinone, tert-butyl-hydroxy anysole, lignosulphonic acid and salts thereof, 6-hydroxy-2,5,7,8-tetra-methylchroman-2-carboxylic acid (Trolox™), 1,2-benzisothiazoline-3-one (Proxel GXL™), a benzofuran or benzopyran derivative (as defined herein), tocopherol sorbate, butylated hydroxy benzoic acid and its salts, gallic acid and its alkyl esters, uric acid and its salts and alkyl esters, sorbic acid and its salts, dihydroxy fumaric acid and its salts, and mixtures thereof.        
Furthermore, in a second aspect the invention provides a method of cleaning a fabric substrate, comprising the steps of treating the substrate with a liquid composition of the present invention in an aqueous environment, rinsing the substrate and drying it.